This invention relates generally to the handling of objects such as, for example, precast concrete panels. The invention has particular though certainly not exclusive application to facelift and edgelift systems for handling large precast building elements, such as concrete panels, in the construction industry.
It is now widespread practice to construct various kinds of buildings, but especially commercial and industrial buildings, by on site erection and assembly of structural concrete panels which are either precast on site and tilted into position, or precast elsewhere and brought to the site In the latter case, the panels are normally cast flat, lifted to the vertical, and then transported while substantially vertical and lifted into position on site.
It is of course imperative in the handling of these large structural panels as they are tilted, transported and moved into position that there be no risk whatever that they will fall. An established system for handling the panels involves an anchor cast in the panel and a clutch assembly by which a crane sling may be secured to the anchor. The anchor normally includes a head within the concrete body and an end which remains below the face or edge of the panel but is exposed within a recess. The clutch engages the anchor within this recess and is arranged so that the clutch cannot disengage while the panel is in a partially or wholly tilted orientation. One such arrangement is disclosed in U.S. Pat. No. 3,883,170 and is the basis of the commercial Frimeda system. Another approach is described in Australian patent 544832.
While these systems with an embedded anchor and safety clutch assembly have proven satisfactory in practice, they do have a significant disadvantage in that the steel anchors remain embedded in the panel in the erected building. In time, even though the original recess is capped or filled with mortar, the embedded steel anchor is a source of corrosion and can lead to discolouring in walls formed from the panels. There is also the economic issue that a relatively heavy steel component is essentially only used once and is in effect discarded because it cannot be practically recovered for reuse.
Any improved panel handling system should preferably be adaptable to both facelift and edgelift systems.
There have been at least two attempts to address these issues by providing a substantially plastic component in the panel. Australian patent 488954 proposes an arrangement in which the anchor component comprises a steel nut contained in an undercut enlargement at the end of a plastic tube cast in situ, and a threaded eyebolt is projected down the tube and attached to the nut for lifting. The steel component is much smaller, but this system has the significant disadvantage of the time required to screw and unscrew the eyebolt. In a somewhat similar approach described in Australian patent application 89982/91, a flat steel rectangular block is provided in an undercut enlargement in a rectangular plastic tube, and a pair of clutch shafts are inserted into the hole deformed by the tube. The shafts have end lugs which engage under the block and the system is locked by pushing in a secondary pin between the shafts to forcibly separate them. This system has been viewed as unsafe for transporting heavy building elements because of the risk of operator error in failing to insert the locking pin.
German patent application 195 23 476 discloses an arrangement in which an anchor body is rotatable to bring a pair of lugs beneath undercuts in a lined cavity, and then locked against return rotation by turning down a notched flap to engage the crane lift bar. Longitudinal voids are provided in the concrete for the passage of the crosshead extensions and lugs during insertion. These voids remain empty during lifting operations, and are a potential source of weakness as they could allow concrete to break away and flow into them. The rotatable load bearing element is a tube, and there is a cross-head spaced from the inner end of the cavity. This system requires, on attachment, four separate manual operations, ie. insertion, rotation, locking and crane hook engagement, and, on detachment, each of these four steps in reverse. Remote release is not an available option.
The present invention proposes four improvements which may be used separately but are preferably used in conjunction, and which are suited to use with an undercut plastic tube former of appropriate profile. One of these improvements is to provide for engagement by way of a limited rotating action, another to provide safety by linear motion of a positively blocking element responsive to the position of the lifting tackle, a third involves proper control of voids and cavities to prevent failure by collapse or flow of material, and a fourth entails a novel configuration of relatively rotatable and non-rotatable elements.
In a first aspect, the invention accordingly provides an object handling device including a support body, and an elongate anchor body mounted at the inner end thereof to the support body so as to project from the support body for insertion into an undercut cavity in an object to be handled and so as to be rotatable about an axis generally parallel to the longitudinal dimension of the anchor body. At least one anchor lug at or adjacent to the outer end of the anchor body is movable by rotation of the anchor body between a first position in which the anchor body is able to be inserted into or withdrawn from the cavity, and a second position in which the lug(s) engage respective undercut shoulder portions in the cavity. Means on the anchor body is engagable for rotating the anchor body to move the anchor lug(s) between the first and second positions. Lift means on the support body is engagable by a crane to lift the object.
Preferably, lock means is responsive to the lift means to block movement of the anchor lug(s) from the second position.
In a second aspect, the invention provides an object handling device including a support body, and elongate anchor body means mounted at an inner end thereof to the support body so as to project from the support body for insertion into an undercut cavity in an object to be handled. At least one anchor lug at or adjacent the outer end of the anchor body means is moveable with the anchor body means between a first position in which the anchor body means is able to be inserted into or withdrawn from the cavity, and a second position in which the lug(s) engage respective undercut shoulder portions in the cavity. Means on the anchor body is engagable for moving the anchor lug(s) between the first and second positions. Lock means is slidable generally longitudinally of the anchor body means to a blocking position in which movement of the anchor lug(s) from the second position is blocked. Lift means carried by the support body is engagable by a crane to lift the object, and means is responsive to the lift means to activate the lock means to slide it to the blocking position.
In a third aspect, the invention provides an object handling device including a support body, and elongate anchor body means mounted at an inner end thereof to the support body so as to project from the support body for insertion into an undercut cavity in an object to be handled. At least one anchor lug at or adjacent the outer end of the anchor body means is moveable with the anchor body means between a first position in which the anchor body means is able to be inserted into or withdrawn from the cavity, and a second position in which the lug(s) engage respective undercut shoulder portions in the cavity. Means on said anchor body is engagable for moving the anchor lug(s) between the first and second positions. Lift means on the support body is engagable by a crane to lift the object, and lock means is responsive to the lift means to block movement of the anchor lug(s) from the second position. In this third aspect, the device is shaped and configured for said insertion so that, when the anchor lug(s) are in said second position, there is substantially no cavity or void in the object within a region outwards of the undercut shoulder portions sufficient to allow collapse or flow of the object material when the object is being lifted.
The invention still further provides an object handling device including a support body, and an elongate anchor body mounted at the inner end thereof to the support body so as to project from the support body for insertion into an undercut cavity in an object to be handled and so as to be rotatable about an axis generally parallel to the longitudinal dimension of the anchor body. At least one anchor lug at or adjacent to the outer end of the anchor body is movable by rotation of the anchor body between a first position in which the anchor body is able to be inserted into or withdrawn from the cavity, and a second position in which the lug(s) engage respective undercut shoulder portions in the cavity. Means on the anchor body is engagable for rotating the anchor body to move the anchor lug(s) between the first and second positions, and lift means on the support body is engageable by a crane to lift the object.The lift means is rotatably mounted with respect to the support body and is thereby rotationally alignable with the direction of load.
In a fifth aspect, the invention is directed to an object handling device embodying the features of two or more of the first, second, third and fourth aspects of the invention.
Preferably, the lock means is a plurality of elongate shafts or pins of cross section similar to and matching the cross section of the respective lugs in a plane normal to the axis. By this arrangement, the lugs are aligned with the lock shafts or pins during insertion or withdrawal of the device, and move out of alignment in the second position, whereupon the lock rods slide into the vacated space and thereby block movement of the lugs back to the first position.
Preferably, the elongate anchor body is generally cylindrical and the lugs and lock rods exhibit dovetail or part annular profiles to opposite sides of the anchor body as viewed in cross section. In one embodiment, particularly suited to edgelift systems, the angular extent of the lugs about said axis is about 60xc2x0 so that the lugs occupy adjacent 60xc2x0 sectors in the respective first and second positions. Alternatively, and more suitably for facelift systems, the lugs sub-tend about 90xc2x0 at the axis of the anchor body and thereby occupy respective 90xc2x0 sectors in their first and second positions.
Said means engagable for moving the anchor body lugs preferably includes a manipulable handle carried by the support body.on the side opposite that from which the anchor body extends.
The lift means is preferably a solid component rotatably carried by the support body for movement between a first position in which the lock means does not block the anchor body lug(s) and a range of rotational positions in which it does. The responsive means is preferably a cam and cam follower arrangement by which the lift means and lock means are engaged in a co-operative relationship. According to the exact nature of the lift system in use, the aforementioned first position for the lift means will be that in which the object being handled is at rest, not elevated, and has with no lifting tension applied to the lift means, while any other position of the lift means will cause activation of the lock means to block the anchor lugs.
Preferably, means is provided to bias the lock means to a position in which it does not block movement of the anchor lugs. Preferably also, means is provided to bias the support body of the lift device clear of the object surface about the cavity unless it is pushed into the cavity and the anchor lugs engaged.
In a sixth aspect, the invention provides a form for defining an undercut cavity in a pre-cast object, said form being in a plastics and/or polymer material or a thin gauge metal, wherein the form includes a first portion defining an elongate passage of substantially uniform cross section including a core portion and respective laterally projecting portions of a predetermined profile, and a pair of undercut portions of cross section geometrically similar to said side portions and disposed adjacent to the respective side portions.
A preferred handling, eg lifting, system according to the invention includes a handling device according to the first, second, third and fourth aspects of the invention and a cavity form according to the sixth aspect.